The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The invention relates to magnetorheological clutches which consist of a stationary part, a rotatable primary part with primary lamellae, and a secondary part with secondary lamellae which is rotatable about a common axis and surrounds the primary part, there being formed between the primary part and the secondary part a space which contains a magnetorheological fluid and in which primary lamellae and secondary lamellae alternate in the axial direction, and a magnet coil generating a magnetic field of regulatable field strength which acts on the magnetorheological fluid.
However, for the use of a generic clutch in the drive train of a motor vehicle, current consumption and overall size are critical and must therefore be minimized. In addition to this, there are also further requirements: such as a wide regulating range of the transmitted torque that, on the one hand, provide slip-free starting from standstill and, on the other hand, (also for reasons of noise), complete separation are possible; and, finally, a rapid response in order to be compatible with electronic drive dynamics controls (ESB, ABS, etc.).
Thus, U.S. Pat. No. 5,845,753 discloses a generic clutch, in which the yokes extend from one end face on one side of the clutch, so as to surround this on the outside, as far as a second end face on the other side of the clutch. This not only increases the diameter and weight, but also means a large mass to be magnetized, thus consuming a large amount of current and resulting in the reduction of the magnetic field (disengagement) lasting too long for a usable control. Moreover, the magnetic force lines which pass through the space filled with the magnetorheological fluid are of low density and are distributed highly unevenly.
The object of the invention is, therefore, to provide a magnetorheological clutch which avoids the disadvantages of the prior art and satisfies the above-specified requirements of the modern motor vehicle. The magnetorheological clutch should have as small a size as possible, particularly in diameter, be capable of transmitting a maximum torque with minimum current consumption, and yet be easily controllable.